Electrical protective



(No Model.)

A. H. McGU'LLOCH. ELECTRICAL PROTECTIVE APPLIANCE.

No. 550,638 Patented Dec. 3, 1895.

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AN DREW GRAHAM PHDTO-UTNRWASHINGTUN. D Cv UNITED STATES PATENT OFEIcE.

ALFRED II. IIIOCULLOCH, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE NEIV ENGLAND TELEPHONE AND TELEGRAPH COMPANY, OF NEW YORK.

ELECTRICAL PROTECTIVE APPLIANCE.

SPECIFICATION forming part of Letters Patent No. 550,638, dated December 3, 1895.

Application filed September 14, 1895. Serial No. 562,524. (No model.)

To aZZ whom it may concern.-

Be it known that I, ALFRED I-I. MCOUL- LOGH, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain Improvements in Electrical Protective Appliances, of which the following is a specification.

The present invention relates to protective appliances interposed at suitable places in electric conductors for the purpose of protecting the same and the apparatus and instruments associated therewith from excessive currents abnormal to the said conductors and apparatus, and especially to the form of pro- I 5 tectivc device which constitutes a portion of a line conductor and which is ruptured by the abnormal current. It is well known that when such a protective device is ruptured by reason of an excessive current upon it va- 2o rious troubles are liable to ensue. For instance, if the device is in the form of a fuse it may explode with a loud report, smoke will issue from the fuse-box, and fire-hazards arise from the drawing of a long are between the 2 5 f use-wire terminals,which is oftentimes maintained for a considerable time. The explosions are sometimes so severe as to rend the fuse-box in pieces and scatter the fragments thereof to a distance, and when an arc is maintained the metal fuse-terminals are destroyed,

and destructive fires may be caused thereby.

I am aware that fuses have been inclosed in tubes of various kinds to prevent the melted fuse material from being scattered about; but

I find that such tubes tend to the making of arcs between the fuse-terminals, from the fact that the resulting gases of an explosion are retained therein and the fuse-wire is vaporized the whole of its length, depending, of course,

upon the strength of current, and when of combustible material the tubes are ignited and increase the fire-danger.

My invention is designed to avoid the abovementioned troubles and annoyances; and it consists of an appliance having a conductor of easily-fusible metal, alloy, or of any other suitable material which may be fused or ruptured and inclosed or surrounded with a porous noncombustible substance or material which will deaden the sound of the explosion of the conductor, prevent particles from scattering, absorb any smoke that may be produced, and confine the destruction of the conductor to a relatively-small portion of its length.

A fusible conductor breaks down at its 5 5 weakest place or place of highest resistance, and under favorable circumstances melts on each side of the break back to the screw-posts or terminals in which it is held. By my invention when the fuse explodes the gases and vapors are allowed instantly to escape laterally through the surrounding porous material. The pressure being thus relieved, there is but little melting of the fuse longitudinally, and, furthermore, by reason of the fact that the vapors or gases are caused to pass through the various interstices of the surrounding porous material the electrical continuity of the said gases or vapors is broken.

In carrying out my invention I prefer to construct the conductor constituting the protective appliance from common fuse-metal, reinforcing the same at its ends, thus raising its capacity to carry electric current thereat, and making the place of highest resistance at 7 5 the center of its length, in order that the explosion or rupture may take place as far from the terminals as possible.- In practice Iconstruct the fuse in the form of a wire or ribbon and turn each end back, winding it around itself, leaving a portion of single wire or other conductor in the center. Thus prepared it is secured at each end to screw-posts or terminals arranged upon a base-board, to which the line conductors are also connected. Over 8 5 the fuse is placed a covering or box, which is secured tothe base-board. I may surround the fuse with a loose porous yielding noncombustible material, such as asbestos, pressing it loosely about the fuse and then secure 0 the covering or box to the base-board. I prefer, however, to use the non-combustible covering in the form of a tube or sheath woven from coarse asbestos yarn, made sufficiently large in diameter for the fuse to slip in easily 5 and woven coarse and yielding enough to I readily expand under moderate pressure.

In the drawings which illustrate the in vention, Figure 1 shows a fuse embodying my invention. Fig. 2 shows the same fuse cov- IOO ered with a porous woven tube or sheath of non-combustible material. Fig. 3 is a section of a box in which afuse is shown secured to terminals upon its base-board and forming a portion of a line-conductor. Fig. 4E illustrates the effect of an explosion of a fuse upon the porous covering. Fig. 5 shows a fuse in its covering, the whole being knotted in the center.

Fig. 1 shows a conductor a of any suitable material, such as a metal or alloy, having the central portion of its length of smaller conducting capacity and consequently of higher resistance than that of its ends. The preferred form of conductor-fuse is a wire or ribbon the ends of which are doubled back upon themselves and twisted for a considerable portion of the entire length of the fuse, leavi ing a comparatively-short part in the central i l easily fusible conductor surrounded by asbes- 1 tos in a loose and porous state.

portion of single wire.

Fig. 3 shows a box consisting of a baseboard cl, provided with line-terminals g, 9 3

1 easily fusible conductor surrounded by a tube and g and a supporting-block e.

The fuse is secured at one end to terminal 9, at which the line enters, and by its other end to terminal 9 at which the line Q02 departs. 10 is a ground-wire connected through the terminal g and carbon blocks 0 to the ter minals g in a well-known manner. A cover f fits over the base-board d and is usually provided with perforations. After securing the fuse a to the terminals I may surround it with a yielding porous non-combustible ma terial, such as asbestos, pressing it gently around the fuse, and then place the cover f upon the base-board. This will answer all of the requirements; but owing to its fieecy nature it is not a neat method.

I prefer to arrange the porous material in the form of a tube or sheath, made of coarse asbestos yarn and woven in a somewhat loose fashion. This tube is marked 0 in the drawings and the fuse is shown as inside thereof, its ends projecting from the tube and 0011- nected with the terminals g. Owing to the loose manner in which it is woven, when a fuse explodes, gases and vapors can force the yarns apart at the point in the wire where it first breaks and escape laterally, as shown by arrows in Fig. 4, 0 representing the bulge in the tube made by the pressure of the escaping gas. The pressure being thus suddenly relieved, the fuse is not usually vaporized or burned to any considerable extent on either side of the first break, and as the vaporized portion of the f use escapes in so many and diverse directions the particles thereof are thoroughly separated and their electrical conductivity is broken.

The primary object of the reinforced ends of the fuse inclosed in such a tube asdescribed is to compel the rupture or explosion to take By the invention prolonged arcs are prevented, comparatively little noise or smoke is produced, and the line-terminals are thoroughly protected.

Fig. 5 shows a fuse covered by an asbestos tube with a knot tied in its central part. The object of the knot, as shown in Fig. 5, is that when the Wire is ruptured byreason of a comparatively feeble foreign current the melted metal will tend to separate and thus break the circuit.

Although I speak of the portion of the conductor between the terminals as a fuse wire or a fusible conductor, meaning thereby any metal or alloy, I may use any suitable conductor for this purpose, such as carbon or other friable substance, which is easily ruptured by an excessive current.

Having now fully described my invention, I claim 1. A protective appliance consisting of an 2. A protective appliance consisting of an of woven asbestos.

3. A protective appliance consisting of a conductor having the central portion of its length of higher resistance than the end portions thereof, surrounded by a woven tube of asbestos.

4. A protective appliance consisting of a fuse surrounded with a tube of woven asbestos, the fuse projecting from each end of the tube, and a knot tied in the central part thereof.

5. A protective device consisting of a fusible wire or ribbon having its ends doubled back and twisted to leave a comparatively short central portion of single wire, as set forth. 4

6. A protective device consisting of a fusible wire or ribbon, having its ends doubled back and twisted, inclosed in atube of woven asbestos, as set forth.

7. A protective fuse consisting of a wire or ribbon of easily fusible metal or alloy attenuated at its middle, and inclosed in a strong tube of Woven or braided asbestos, constituting a non-conductin g and incombustible fuse envelope, adapted to prevent arcing and the escape of molten metal, and to facilitate the separation of the vaporous or gaseous particles.

8. A protective fuse comprising a section of easily fusible conductor smaller at its middle than at its ends, combined with a noncondueting, incombustible sheath applied thereto and surrounding the same, the said sheath being loose and porous for the ready escape of gases, substantially as described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 6th day of September, 1895.

ALFRED II. MCOULLOOII.

IVitnesses Gno. WILLIS PIERCE, J OSEPH A. GATELY. 

